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Original Investigation
March 6, 2019

Early Melanoma Nodal Positivity and Biopsy Rates Before and After Implementation of the 7th Edition of the AJCC Cancer Staging Manual

Author Affiliations
  • 1Division of General Surgery, Vanderbilt University Medical Center, Nashville, Tennessee
  • 2Department of Dermatology, Vanderbilt University Medical Center, Nashville, Tennessee
  • 3Division of Surgical Oncology and Endocrine Surgery, Vanderbilt University Medical Center, Nashville, Tennessee
JAMA Dermatol. 2019;155(5):572-577. doi:10.1001/jamadermatol.2018.5902
Key Points

Question  Are the staging criteria in the 7th edition of the AJCC Cancer Staging Manual (AJCC 7) associated with changes in the distribution of thin melanomas for patients undergoing nodal surgery and for patients with positive nodes?

Findings  In this cross-sectional study of 86 846 patients diagnosed before AJCC 7 (2004-2009) and of 54 434 patients diagnosed after AJCC 7 (2010-2013), there was a decrease in the number of nodal surgeries performed and an increase in the number of patients with T1b melanomas undergoing nodal surgery.

Meaning  Our results suggest that more patients were upgraded to T1b melanomas and fewer nodal biopsies were performed without clinically significant change in nodal positivity rates.

Abstract

Importance  There has been a continued increase in the incidence of newly diagnosed melanomas, most of which are T1 melanomas. The associations between changes in tumor staging, implemented with the 7th edition of the AJCC Cancer Staging Manual (AJCC 7), and sentinel lymph node biopsy rates and nodal positivity rates remain to be seen.

Objective  To evaluate the change that the implementation of the AJCC 7 had on staging criteria and the distribution of thin melanomas requiring nodal surgery and nodal positivity rates.

Design, Setting, and Participants  Retrospective cross-sectional study from 2004 through 2013 of all adults (≥18 years) diagnosed with a T1 (Breslow depth ≤1.0 mm) melanoma using The National Cancer Database that captures 70% of all newly diagnosed cancers from accredited Commission on Cancer organizations, including both academic and community settings. Data were analyzed in May 2017.

Exposures  Patients were grouped together based on year of diagnosis, before and after 2009.

Main Outcomes and Measures  To determine the sentinel lymph node biopsy rate before and after the implementation of the AJCC 7.

Results  A total of 141 280 patients met inclusion criteria. Of 86 846 patients diagnosed from 2004 through 2009, 53.7% (49 644) were male and had a mean (SD) age of 57.7 (16.4) years. Of 54 434 patients diagnosed from 2010 through 2013, 54.3% (31 086) were male and had a mean (SD) age of 59.5 (15.9) years. After 2010, there was a 3.8% decrease in the number of nodal surgeries performed (32 485 of 86 846 patients [37.6%] vs 18 379 of 54 434 patients [33.8%]; P < .001). The nodal positivity rate decreased 1.0% from (9.8% [3166 of 86 846] to 8.8% [1618 of 54 434]) (P < .001). An increase in the proportion of T1b melanomas being evaluated, from 48.8% to 62.2%, was seen (P < .001). Of T1b melanomas that underwent nodal evaluation from 2004 through 2009, 74.0% had Clark level IV (invasion of the reticular dermis) or Clark level V (invasion of the deep, subcutaneous tissue) and 9.5% were ulcerated. From 2010 through 2013, of the T1b melanomas undergoing nodal evaluation, 82.6% had an elevated mitotic rate only, 3.7% were ulcerated, and 13.7% had both ulceration and an elevated mitotic rate.

Conclusions and Relevance  It appears that after the institution of AJCC 7, there was an overall decrease in the number of T1 melanomas undergoing nodal biopsy without a clinically relevant change in sentinel lymph node positivity, with an increase in the number of T1b melanomas undergoing nodal evaluation.

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